This invention is concerned with an improved herbicide composition of the wettable powder or dry flowable type and a process for making it.
Chemical herbicide compositions which are effective against a variety of weed species are conventionally formulated either as aqueous solutions, emulsifiable concentrates, dusts or granular particles.
Subspecies of the dust and granular particle type formulations are formulations which are designated as wettable powder or dry flowable formulations. Wettable powders or dry flowable formulations are dry compositions which are intended to be suspended as slurries and sprayed on the target, using well known techniques. These powders generally contain from about 20 to about 95% by weight active pesticide ingredient, up to about 80% by weight dispersible and/or soluble inert diluents such as clays vermiculite, carbon black, and the like, and from about 1 to about 10% by weight of surfactants and dispersants for promoting rapid wetting and dispersing water and disperability in the spray tanks. Wettable powder formulations or dry flowable formulations are normally prepared by incorporating the active herbicide or pesticide with the diluent carriers which absorb the active ingredients, and then the diluent carriers with the absorbed active ingredients are hammer milled to produce powders of the granule size desired.
There are a number of problems associated with the preparation of a wettable powder or dry flowable formulation. Specifically, it is not always possible to mill the active ingredient absorbed onto the diluent carrier to the optimum size. In addition, the inclusion of a dispersant in the formulation sometimes competes with the absorption process between the active ingredients and the carrier. Further, some dispersants or emulsifiers which are used are toxic to humans or animals with which they come into contact and require warning labels to be applied to the product which restricts the breadth of use possible.